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Surfactant concentration profile at the interface of two fluids in Fluent (VOF)

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Old   May 29, 2020, 08:30
Default Surfactant concentration profile at the interface of two fluids in Fluent (VOF)
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I am working on a two-phase (liquid-liquid) flow problem. I have an experimental data of changing interfacial tension (surface tension) for increasing the surfactant concentration. I feed the interfacial tension value (fixed) during the simulation and run the simulation. I have matching simulation and experimental data.

Now, I would like to generate the surface concentration profile at the interface using the interfacial tension value in Fluent using the Gibbs equation (liquid-liquid) at a fixed temperature. Kindly advice how this can be implemented in Fluent.
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Old   May 29, 2020, 10:47
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Your query is not very clear, however, if you want to implement variation in surface tension based on some other field variable, such as, temperature, then you will have to either use an expression or a UDF. Since surface tension is a property, you will have to use DEFINE_PROPERTY macro.
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Old   May 29, 2020, 15:52
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What is unclear to you? I can explain.
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Old   May 29, 2020, 15:55
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What exactly do you want to do? And at what step do you need help?
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Old   May 29, 2020, 22:48
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In my case the interfacial tension vary between 12mN/m2 to 18mN/m2. I do seperate simulation for every value and extract the simulation data. In practical case, this change in interfacial tension is because of adding surfactant at different concentration to one of the fluid. Gibbs equation relates this d(gamma)/d(ln C) = Tow. Where gamma is interfacial tension, C is surfactant concentration and Tow is surface concentration of surfactant (at Interface) . I have only gmma value. I should generate contour profiles of C at the interface. In my case the interfacial tension is a fixed value throughout the simulation. Hope this is clear.

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Old   May 30, 2020, 08:39
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It looks more like a post-processing issue. If you want to plot concentration profile at the interface, then you can just create an interface using volume fraction and plot mass fraction contours. If you want a single, averaged value, then you can use area-averaged value of mass fraction at the interface.

From your first post, it appears that you want to use the outcome as an input to the system, so that it could affect the solution. If that is the case, then you will have to use UDF.
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